Blow-molding is a common technique for forming plastic (or other non-porous material) containers, such as bottles or flasks. Plastic is the conventional choice for blow-molding because of its thermal properties and its lack of porosity. Typical plastic containers begin as an injection-molded or extruded preform that is preheated and placed into a mold formed in the shape of the container. To achieve final shape, a rod is disposed in the preheated preform, stretching it to about the length of the mold. Once the preform is sufficiently stretched, a blast of air is dispensed therein which pushes the walls of the preform against the inner surface of the mold. The resulting shape of the preform becomes that of the desired container.
The lack of porosity in plastic makes it receptive to force produced by the air. In contrast, natural fiber structures, such as randomly oriented fiber mats, are not conducive to blow-molding because they are extremely porous. If blow-molding a fibrous substrate is attempted conventionally, the forced air simply penetrates and passes through the substrate's pores and interstices. The force of air will fail to push the mat into the molded shape.
Accordingly, an illustrative embodiment of the present disclosure provides a blow-molded composite comprising first and second fibrous layers and first and second film layers. The first fibrous layer comprises randomly oriented fibers dispersed throughout the thickness of the layer and having first and second surfaces. The first film layer has first and second surfaces such that the second surface of this layer is bonded to the second surface of the first fibrous layer. The second film layer has first and second surfaces as well, but only a portion of the first surface is bonded to the first surface of the first film layer. In addition, at least one cavity exists between the first and second film layers. The second fibrous layer also comprises randomly oriented fibers dispersed throughout the thickness of the layer and has first and second surfaces. The first surface of the second fibrous layer is bonded to the second surface of the second film layer.
In the above and other illustrative embodiments, the blow-molded composite may further comprise: the fibers being selected from a group consisting of synthetic fibers and natural fibers, and wherein the fibers are present in an amount ranging from over 0% to about 70%; the first and second fibrous layers comprising a binder that is bonded with the fibers; the binder being selected from a group consisting of polypropylene, polyester, nylon, and polyethylene, and wherein the binder is present in an amount ranging from over 0% to about 70%; the first and second films resist bonding at about their melting temperatures; the first and second films comprising nylon-6 and nylon-66; the second surface of the first film layer and the first surface of the second film layer comprising a corona surface, and wherein the first surface of the first film layer and the second surface of the second film layer are non-corona surfaces; the first fibrous layer comprising a weight of about 800 grams per meter square to about 3000 grams per meter square, fibers being natural or synthetic fibers present in an amount ranging from above 0% up to about 70% of formulation; the binder being polymer fibers present in an amount ranging from about 30% up to about 70% of formulation, and a needle punch density from about 20 per square centimeter up to about 80 per square centimeter; the second fibrous layer comprising a weight of about 800 grams per meter square to about 3000 grams per meter square, fibers that are natural or synthetic fibers present in an amount ranging from about 30% up to about 60% of formulation, the binder being polymer fibers present in an amount ranging from about 40% up to about 70% of formulation, and a needle punch density from about 20 to about 65 per square centimeter.
Another illustrative embodiment of the present disclosure provides method of blow-molding a fibrous composite. The method comprising the steps of: providing upper and lower fiber layers each comprising randomly oriented fibers and a binder dispersed throughout the thickness of each layer, and each having first and second surfaces; providing upper and lower film layers, each having first and second surfaces; placing the first surface of the upper film layer adjacent the second surface of the upper fiber layer; placing the second surface of the lower film layer adjacent the first surface of the lower fiber layer; locating the lower fiber and film layers on a lower blow-mold plate having a surface, and comprising at least one protrusion extending from that surface and at least one fluid passage disposed in the plate; applying a vacuum through the passage between the surface of the lower blow-mold plate and the lower fiber layer; drawing the lower fiber and lower film layers against at least a portion of the surface of the lower blow-mold plate; piercing the lower fiber and lower film layers with a pin having an opening disposed therein; extending the opening beyond the first surface of the lower film layer; placing the first surface of the upper film layer against the first surface of the lower film layer forming a cavity around at least a portion of the pin between the first surfaces of the upper and lower film layers; applying pressure against the upper fiber and film layers against the lower film and fiber layers; and blowing fluid from the opening into the cavity to cause at least the lower film and fiber layers to take the shape of the lower blow-mold plate and bond the first and second films together.
In the above and other illustrative embodiments, the blow-molded composite may further comprise: heating the upper and lower fiber layers prior to placing the upper and lower film layers thereon; the film layers lying together but not sticking together; blowing fluid from the opening into the cavity wherein the fluid is a gas; sealing the periphery of the upper and lower fiber and film layers prior to blowing fluid; locating the lower fiber and film layers on a lower blow-mold plate having a surface, and comprising a plurality of protrusions extending from that surface and a plurality of fluid passages disposed in the plate; locating a clamp finger onto the first surface of the second film layer prior to blowing fluid from the opening; drawing down at least a portion of the pin to cause the lower film to form a seal around the pin prior to blowing fluid from the opening into the cavity; continuing to draw a vacuum against the lower fiber layer while blowing fluid into the cavity
Additional features and advantages of this disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrated embodiment exemplifying the best mode of carrying out the disclosure as presently perceived.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates embodiments of the blow-molding composition and method, and such exemplification is not to be construed as limiting the scope of the blow-molding composition and method in any manner.